Arkansas Game and Fish- dead fish were drumfish (bottom feeders). Some collected were sick. Some were sent to the Univ. Arkansas lab at Pine Bluff for examination. Disease is suspected. Keith Stevens of the Commission said only drumfish were affected.

The Game and Fish Commission suspects revelers shooting off fireworks were the cause of the blackbirds deaths. They were startled off their roosts started to fall about 11:30 PM. Some showed internal bleeding from collisions and stress may have killed others. No poison found.
(AP says 1000 birds, CBS says 2000, CNN says 5000.)

Above from reports in The Daily Telegraph, Jan. 3.